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m-BROMOBENZOIC ACID

in

m-Ainixiobenzoic Acid

20 gnns. nitrobenzoic acid.

40           granulated tin.
120   c.c.    cone, hydrochloric acid.

The nilrobenzoic acid, tin, and hydrochloric acid are mixed
 a litre flask and wanned until the reaction begins. When
the first vigorous action is over, the mixture is heated on the
water-bath until the tin is dissolved. The liquid is poured
into a basin and evaporated on the water-bath to expel the
excess of hydrochloric acid. The tin is then precipitated by
passing' into the hot, dilute solution a current of hydrogen
sulphide. The sulphide is filtered and washed with hot water,
and the filtrate evaporated to dryncss. To obtain the free acid,
a small portion of the residue is dissolved in very little water
made alkaline with ammonia, and acidified with acetic acid.
It is recrystallised from water, and melts at 174.

m-Hydroxybenzoic Acid,

15 grms. ;//-;iminobenzoic acid hydrochloride (in 200 c.c. water).
6*5         sodium nitrite (in 15 c.c. water).

The nitrite solution is slowly added to the solution of the
hydrochloride dissolved in water. The liquid is heated on
the water-bath until the evolution of nitrogen ceases, and then
filtered and concentrated. The hyclroxybenzoic acid separates
on cooling as a brown mass, which may be purified by dissolving
in water and boiling with animal charcoal. It separates in
colourless crystals, in. p. 200. Yield, 7 grams, See Appendix,
P- 33-

PREPARATION 92.

m-Bromobenzoic Acid,  C(!H/5jL          l

v

Hiibner, Petermann, Anmilen, 1869, 149, 131.
5 grins, benzoic acid.
7          bromine.
30 c.c. water.
The mixture is brought into a thick-walled tube, closed at one
end and sealed in the usual way.    The tube is heated in the